1. Field of the Invention
The present invention relates to semiconductor devices and, particularly, to a semiconductor device package and a method of making the same.
This application is a counterpart of Japanese application Serial Number 2000-347855, filed on Nov. 15, 2000, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
FIG. 10 shows a conventional ball grid array (BGA) type semiconductor device. The BGA type semiconductor device comprises an insulative board 51 and a plurality of metal bumps or solder balls 52 arranged on the lower face of the insulative board 51 as outer electrodes so that it makes miniaturization possible and stronger and easier to handle than the pin type package. Also, it comprises a plurality of conductive members or metal foils 53 and conductive members 54 and 55. A solder resist 56 is provided on the lower face of the insulative board 51. A semiconductor element 58 is bonded to the upper face of the insulative board 51 with a bonding agent 57. The electrodes 59 of the semiconductor element 59 are connected to the conductive members 53 by metal wires 60, which are covered by an insulative resin 61.
However, the BGA type semiconductor device has the solder resist 56 to coat the lower face of the insulative board 51 so that if the solder resist 56 has low adhesive powers, it could separate to lower the reliability of the semiconductor device. Since the insulative board 51 already has the conductive members 53, 54, and 55, the solder resist 56, and the metal bumps 52, the manufacturing cost is high.
Accordingly, it is an object of the invention to provide a simple, inexpensive, and reliable semiconductor device having advantages of the BGA type semiconductor device, such as miniaturization, strength, and easiness to handle.
According to one aspect of the invention there is provided a semiconductor device which comprises an insulative board having first and second opposed faces; a thermally plastic resin provided on the first face of the insulative board; a semiconductor element secured to the first face of the insulative board by the thermally plastic resin and having at least one electrode; at least one metal wire having an end bonded to the electrode of the semiconductor element and the other end put through the thermally plastic resin and the insulative board to form a metal ball that is embedded in the insulative board on a side of the second face of the insulative board; an enveloping resin for enveloping the metal wire on a side of the first face of the insulative board, and at least one metal bump provided on the second face of the insulative board and connected to the metal ball.
According to an embodiment of the invention, the insulative board has a tape-shaped form.
According to another embodiment of the invention the insulative board is curable with ultraviolet rays.
According to still another embodiment of the invention, the insulative board is made of nonwoven cotton fabric.
According to another aspect of the invention there is provided a method of making a semiconductor device which comprises the steps of coating a first face of an insulative board with a thermally plastic resin; bonding a semiconductor element onto the thermally plastic resin; piercing the thermally plastic resin and the insulative board with at least one capillary that holds a metal wire, forming a metal ball at a front end of the metal wire on a side of a second face of the insulative board that is opposite to the first face of the insulative board and pulling out the capillary from the insulative board and the thermally plastic resin such that the metal ball is embedded in the insulative board; pressing the capillary onto an electrode of the semiconductor element to bond the metal wire to the electrode and cutting off an extra wire; and attaching at least one metal bump to the second face of the insulative board so as to be connected to the metal ball.
According to still another aspect of the invention there is provided a method of making a semiconductor device, comprising the steps of applying a coat of thermally plastic resin to a first face of an insulative board that is curable with ultraviolet rays; bonding a semiconductor element onto the thermally plastic resin; piercing the thermally plastic resin and the insulative board with at least one capillary that holds a metal wire, forming a metal ball at a front end of the metal wire on a side of a second face of the insulative board that is opposite to the first face of the insulative board and pulling out the capillary from the insulative board and the thermally plastic resin such that the metal ball is embedded in the insulative board; pressing the capillary onto an electrode of the semiconductor element to bond the metal wire to the electrode and cutting off an extra wire; irradiating the insulative board with the ultraviolet rays; and attaching at least one metal bump to the second face of the insulative board so as to be connected to the metal ball.
According to yet another aspect of the invention there is provided a method of making a semiconductor device, comprising the steps of coating a first face of an insulative board of nonwoven cotton fabric with a thermally plastic resin; bonding a semiconductor element onto the thermally plastic resin; piercing the thermally plastic resin and the insulative board with at least one capillary that holds a metal wire, forming a metal ball at a front end of the metal wire on a side of a second face of the insulative board that is opposite to the first face of the insulative board and pulling out the capillary from the insulative board and the thermally plastic resin such that the metal ball is embedded in the insulative board; pressing the capillary onto an electrode of the semiconductor element to bond the metal wire to the electrode and cutting off an extra wire; and attaching at least one metal bump to the second face of the insulative board so as to be connected to the metal ball.
According to yet another embodiment of the invention, the capillary piercing step is performed while the thermally plastic resin is heated on a heat stage.
According to another embodiment of the invention, the metal ball of the metal wire is formed by a spark produced between the metal wire and an electric torch.